The present invention relates to a method for manufacturing a semiconductor device, and relates in particular to a method for manufacturing a semiconductor device whereby a smaller mounting area can be provided by reducing the external size of a package without using lead forming, and a considerable reduction in manufacturing costs can be realized.
In the processing for the manufacture of a semiconductor device, the quality of each semiconductor chip formed on a wafer is determined; excellent semiconductor chips are separated from the wafer by dicing and are bonded to a lead frame; the semiconductor chips bonded to the lead frame are sealed by transfer molding using a die and resin injection process; and the sealed semiconductor chips are separated to provide individual semiconductor devices. A strip-shaped or hoop shaped frame is employed as the lead frame, but regardless of which frame is used, a single sealing process is used to simultaneously seal a plurality of semiconductor devices.
FIG. 13 is a diagram showing the process for checking semiconductor chips formed on a wafer. During this process, the quality of each semiconductor chip 1 formed on a wafer 15 is determined. First, the position of the wafer is recognized, and a needle 14 of a probe is fed a distance equivalent to the chip size and is brought into contact with the electrode pad of a semiconductor chip 1. In this state, an input signal wave, which is programmed in advance, is received from an electrode pad, and the output terminal emits a constant signal wave. A tester reads this signal and determines the quality of the semiconductor chip 1. And when the semiconductor chip 1 is determined to be defective, a mark is provided for it, so that when a recognition camera identifies this mark during the process performed to bond the semiconductor chip 1 to the lead frame, the defective semiconductor chip 1 can be removed.
FIG. 14 is a diagram showing a transfer molding process. During this process, the semiconductor chip 1 fixed to a die pad of a lead frame 2 by die bonding or wire bonding is mounted inside a cavity 4, formed of an upper and a lower die 3A and 3B, and an epoxy resin is injected into the cavity 4 to seal the semiconductor chip 1. Once the process has been completed, the lead frame 2 is cut to complete the fabrication of a separate semiconductor device (e.g., Japanese Patent Publication No. H05-129473).
For this process, as is shown in FIG. 15, multiple cavities 4a to 4f, a resin source 5 for injecting a resin, a runner 6, and gates 7 for injecting the resin into the cavities 4a to 4f via the runner 6, are formed in the surface of the die 3B. For example, if ten semiconductor chips 1 are mounted on a single lead frame, ten cavities 4, ten gates 7 and one runner 6 are formed for one lead frame. And the cavities 4 equivalent to, for example, twenty lead frames are formed in the inner surfaces of the die 3.
Following the transfer molding process, the semiconductor chips 1 are cut off the lead frame and are separated to form semiconductor devices. These semiconductor devices are sorted in accordance with the characteristics (the hfe ranks) detected during the measurement process, and after being taped, are shipped.
FIG. 16 is a diagram showing a semiconductor device obtained by transfer molding. The semiconductor chip 1 whereon elements, such as transistors, are formed is securely attached to an island 8 of the lead frame by a brazing material 9, such as solder; the electrode pad of the semiconductor chip 1 is connected to a lead terminal 10 by a wire 11; the periphery of the semiconductor chip 1 is covered with a resin 12 that conforms to the shapes of the cavities 4; and the distal end of the lead terminal 10 is extended outside the resin 12.
According to the conventional method for manufacturing separate semiconductor devices using transfer molding, since following the completion of the transfer molding the semiconductor chips are cut off and separated into semiconductor devices, a process to determine the characteristic of each semiconductor device must be performed while the semiconductor devices is aligned in a specific direction, and time is required for an extra process.
To resolve the problems, according to the invention, while an insulating substrate made of glass epoxy or ceramic, on which multiple semiconductor chips are mounted, is glued to an adhesive sheet, the semiconductor chips are diced. And without the chips being separated into individual semiconductor devices, a recognition camera identifies the position of a substrate electrode for one semiconductor device, and the characteristic (hfe rank) is determined for the semiconductor device whose position is identified, while the positions of a plurality of semiconductor devices located around it are not identified.
Further, according to the invention, since an insulating substrate made of glass epoxy or ceramic is employed, the extension/contraction ratio is greater than a conventional substrate and the intervals between the substrates are slightly shifted. Thus, when the field of view of the recognition camera is set by masking so it equals in size one semiconductor device, the position recognition precision can be improved. Furthermore, when there is a reduction in the area covered, the time required for position recognition can be reduced.
In addition, according to the invention, the positions of the recognition camera and the needle of the probe, which are used for semiconductor device measurement, are fixed, while the substrate whereon the semiconductor devices are mounted is moved. Therefore, both position recognition precision and work speed can be increased, so that the characteristics of a large number of semiconductor devices can be measured extremely easily. Moreover, when the electrode pad of one semiconductor device is identified, and when the distance shifted from the target position is obtained by an image forming apparatus and the next semiconductor chip is moved while taking the obtained distance into account, position recognition can be performed while corrections are constantly provided for the position shifting.